Risk of venous thromboembolism and endocrine therapy in older women with breast cancer in the United States

Our aim was to evaluate the risk of venous thromboembolism (VTE) with tamoxifen and aromatase inhibitor in older women with breast cancer in the United States. The SEER-Medicare-linked database (2007--2013) was used for women of at least 65 years of age diagnosed with breast cancer in the United States. Logistic regression was used to examine unadjusted and adjusted odds ratios (OR) with 95% confidence intervals (CIs) for the risk of VTE. There were 178 059 women aged at least 65 years with breast cancer in the United States. Twenty-two thousand and forty-two (12.4%) women received tamoxifen, 64 384 (36.2%) women received aromatase inhibitors and 17 419 (9.8%) women received chemotherapy. Adjusted OR = 1.18 (95% CI 1.05--1.32) for VTE with tamoxifen for 3 years or less compared with tamoxifen use more than 3 years and OR = 1.07 (95% CI 1.05--1.16) for VTE with aromatase inhibitors 4 years or less compared with aromatase inhibitors use for more than 4 years. White women had OR = 1.19 (95% CI 1.05--1.35) and black women had OR = 1.07 (95% CI 0.76--1.51) for VTE with 3 years or less tamoxifen use compared with longer use. White women had OR = 1.09 (95% CI 1.00--1.18) and black women had OR = 1.07 (95% CI 0.86--1.34) for VTE with 4 years or less aromatase inhibitors use compared with longer use. Chemotherapy was associated with an increased risk of VTE (OR = 1.77, 95% CI 1.69--1.86). Chemotherapy combined with tamoxifen had OR = 1.64 (95% CI 1.45--1.86) and chemotherapy combined with aromatase inhibitors had OR = 1.71 95% CI 1.59-1.84). The study may help to identify a treatment profile for VTE risk that may facilitate VTE prevention.